A senior climatologist with Environment Canada says the country should expect a cold winter, but warns that forecasting is getting more and more difficult.

"It's almost as if you can't look at the past to tell us what the future is," David Phillips told CBC News.

"There's a new norm: Expect the unexpected."

Phillips said the long-term models show that most of the country will be colder than normal because of La Nina, El Nino's lesser known counterpart.

El Nino and La Nina are two phases of a semi-regular temperature cycle in the tropical Pacific Ocean: El Nino is characterized by warmer-than-normal ocean surface temperatures in the eastern Pacific, while La Nina occurs when the ocean is cooler than normal.

These fluctuations in water temperature affect the air pressure above the ocean and have a dramatic impact on the weather around the Pacific Ocean and the world.

This winter, that should mean cold temperatures.

"Southeastern Canada might see not as cold a winter to begin with," Phillips said.

"But I think that our models are also showing that towards the end of the winter … we see most of the country either being colder than normal, or near normal."

But within this "normal" range is increasingly unpredictable weather.

A new climate study done by Princeton University in New Jersey shows that periods of sunshine and rainfall have become more volatile — erratic patterns of sun and rain have increased 25 per cent in 25 years. It's the first study to examine climate change by looking at variations in daily weather.

David Medvigy, the study's lead author, said the erratic weather will even affect the air we breathe.

"Because of these shifts in sunshine and rainfall, plants will have different rates of photosynthesis," he said. "They'll take carbon dioxide out of the atmosphere at a different rate."

Changing the amount of carbon dioxide could lead to more greenhouse gas in the atmosphere, the study says.